S-b-s compositions

ABSTRACT

Use of compositions prepared with organic coupling agents carrying epoxy groups for preparing applications requiring simultaneously improved mechanical properties and low viscosity.

[0001] The present invention relates to styrene-butadiene-styrenecompositions coupled with organic coupling agents carrying epoxy groups,and their use for various applications such as for example roofing,binders for road coverage or footwear compounds.

[0002] The bituminous compositions of the prior art, when used forroofing or waterproofing membranes suffer from major drawbacks; eitherthe high temperature properties are improved at the expense of the lowtemperature properties, or if both ends of the temperature spectrumyield acceptable performances, the viscosity will be very high,requiring that special equipment be used for handling the bituminouscomposition.

[0003] It is moreover well-known that the residue of the coupling agentremains in the copolymer formed and is thus capable of leaving toxicresidues or other unwanted products in the polymers, which may betroublesome in certain uses. This phenomenon is particularly importantwith silicon tetrachloride (SiCl₄) as coupling agent. Indeed, when SiCl₄is used as coupling agent, it is noted that lithium chloride (LiCl) isformed as by-product. The presence of LiCl is detrimental to the opticalproperties of copolymers and favours the thermal ageing of thesecopolymers.

[0004] It is known to improve the physical properties of bituminouscompositions by incorporating elastomeric block copolymers generallyrepresented by the formula (S—B)_(n)Y wherein Y is the residue of apolyfunctional coupling agent, (S—B) represents a single arm constitutedof a polydiene block B and a polyvinyl aromatic end block S, and nrepresents the number of arms (S—B).

[0005] The coupling agents can be selected from among polyvinyl aromaticcompounds, polyepoxides, polyisocyanates, polyamines, polyaldehydes,polyhalides, polyanhydrides, polyketones, polyepoxyesters andpolyesters. Combinations of different kinds of coupling agents may alsobe used.

[0006] Among the several polyfunctional agents of coupling available onthe market, those of small residual toxicity have been preferred. Forexample, EP-B-344140 discloses the use of polyfunctional coupling agentsof the general formula SiX_(n)R_(4-n) wherein X is a halogen, preferablyCl, R is an alkyl, cycloalkyl or aryl radical, preferably methyl, ethyland/or phenyl and n is an integer from 2 to 4. The most frequently usedcoupling agent is SiCl₄.

[0007] It is also known to use organic coupling agents carrying epoxygroups. Polymers of epoxidised hydrocarbons are used such as epoxidisedliquid polybutadiene or epoxidised vegetable oils such as epoxidisedsoybean oil and epoxidised linseed oil. Each epoxy can be coupled to achain. The number of coupling sites is undetermined and can varyaccording to the number of epoxy groups: it is at least 3 andpreferably, it is from 4 to 6. However, the styrene-butadiene-styrene(S—B—S) compositions obtained with epoxidised triglyceride esters, soldunder the name of Vikoflex, have never been used for commercialapplications wherein good mechanical properties combined with lowviscosity are required.

[0008] It is an object of the present invention to use organic couplingagents carrying epoxy groups in order to prepare products combiningimproved mechanical properties and low viscosity.

[0009] It is another object of the present invention to use organiccoupling agents carrying epoxy groups in order to provide improvedroofing compositions.

[0010] It is a further object of the present invention to use organiccoupling agents carrying epoxy groups in order to provide improvedbinders for road coverage applications.

[0011] It is yet a further object of the present invention to useorganic coupling agents carrying epoxy groups in order to produceimproved thermoplastic compounds.

[0012] The resinous thermoplastic block polymers used in the presentinvention are of the radially branched type with at least 3 arms. Thearms of each branch are composed of substantially pure homopolymericblocks of polymonovinylarene represented by S and polyconjugated dienerepresented by B.

[0013] Preferably, in the process of polymerisation used for preparingthe products of the present invention, a block base copolymer isprepared by the following steps:

[0014] 1) A first block of vinylaromatic monomer is polymerised to forma first block S. 2) The polymerisation is carried out at a temperatureof from 20 to 60° C., for a period of about 20 minutes, in the presenceof an organolithium compound as a catalyst, and in the presence of asolvent that is an inert hydrocarbon.

[0015] 3) When all the vinylaromatic monomer has been polymerised, amonomer of a conjugated diene is introduced into the solution. Thismonomer starts reacting entirely at the living ends of the chains togive a block copolymer of the type S—B—Li, in which B represents theconjugated diene block.

[0016] The vinylaromatic compound which constitutes the block S of theblock copolymer can be styrene, vinyltoluene, vinylxylene orvinylnaphtalene or a mixture thereof.

[0017] The conjugated dienes employed ordinarily are those of 4 to 12carbon atoms per molecule, with those of 4 to 8 carbon atoms preferredfor availability. Such monomers include 1,3-butadiene, isoprene,2,3-dimethyl-1,3-butadiene, piperylene, 3-butyl-1,3-octadiene,2-phenyl-1,3-butadiene, and the like. The monovinylarenes employedordinarily contain 8 to 20, more conveniently 8 to 12 carbon atoms permolecule, including such as styrene, α-methylstyrene, 1-vinylnaphtalene,2-vinylnaphtalene, as well as alkyl, cycloalkyl, aryl, alkaryl, andaralkyl derivatives thereof in which the total number of carbon atoms inthe combined substituents generally is not greater than 12. Examples ofsustituted monomers include 3-methylstyrene, 4-n-propylstyrene,4-cyclohexylstyrene, 4-dodecylstyrene, 3-ethyl4-benzylstyrene,4-p-tolystyrene, or 4-(4-phenyl-n-butyl)styrene.

[0018] The catalyst is generally an alkyllithium, which may be branchedsuch as those of secondary alkyl radicals, having 3 to 8 carbon atoms.However, n- and s-butyllithium are preferably used for reasons of easeof procurement and storage stability.

[0019] The solvents used are generally paraffinic, cycloparaffinic andaromatic hydrocarbons and their mixtures. Examples are n-pentane,n-hexane, n-heptane, 2,2,4-trimethylpentane, cyclohexane, cyclopentane,benzene, toluene and xylene. A polar solvent, such as cyclic esters(THF) or acyclic ethers or tertiary amines, can be incorporated in orderto obtain the formation of a specific polymeric microstructure, such as,for example, an increased amount of vinyl units, as well as random S/Bblocks.

[0020] The peak molecular weight Mp of the base copolymer was measuredby conventional Gel Permeation Chromatography (GPC) technique. The peakmolecular weight Mp, so determined, varies within wide limits and isgenerally from 40000 to 120000 and preferably from 60000 to 80000, thepolyvinylaromatic block representing from 15 to 45% by weight of thebase copolymer. When this stage of the process has been reached,polymeric chains of the type S—B—Li have been formed.

[0021] The operating conditions for the GPC technique were as follows:the temperature was 23° C., the solvant was THF and there were 5 columnsin series containing ultrastyragel with pore openings ranging from 500to 1000000 A. The solvant debit was 1 ml/min and there was a U.V.detector in series with a refraction index detector. 200 microlitres ofthe products to be analysed, at a concentration of 0.1% in THF, wereinjected. The internal standard was 0.01% of tertiobutyl hydroxy toluene(THB) and the calibration was achieved using the Mark and Houwinkequation in which k=1.251E−4 and α=0.717. The calculations were basedupon the refraction index detector and the styrene percentage wasdefined by the U.V. detector.

[0022] The block base copolymer terminated by a lithium atom, called theliving base polymer, is then reacted with at least one coupling agentcomprising at least 3 epoxy groups per mole, preferably at a rate of 0.2to 0.75 parts per hundred parts of the total polymers obtained bycoupling.

[0023] The polyfunctional treating agent is added to the polymerisationmixture under reaction conditions sufficient to form branched copolymerscontaining both the elastomeric and non-elatomeric blocks. Thus thepolyfunctional, treating agent is added to the polymerisation mixtureafter the polymerisation has been essentially completed but prior todeactivation of the polymerisation initiator because it must be able offorming branched polymer by reacting with active terminal lithium atomsof the living polymer.

[0024] The styrenic content of the product is from 15 to 45 weightpercent, preferably from 35 to 39 weight percent, and its peak molecularweight Mp as measured by conventional GPC technique is from 80000 to400000, preferably from 320,000 to 380,000.

[0025] Among the coupling agents that may be used, one may cite theagents of the epoxidised vegetable oil type, the epoxidisedpolybutadiene or even the epoxidised tetrallylether pentaerythritol.Polyepoxidised vegetable oils such as epoxidised soybean oil orepoxidised linseed oil comprising at least 3 epoxy groups per mole,preferably 4 to 6 epoxy groups per mole, will preferably be chosen. Theycan thus couple at least 3 chains. The number of chains coupled by theepoxy groups of the coupling agent is a function of the ratio betweenthe amount of base polymer and the amount of coupling agent. Preferably,5 chains are coupled.

[0026] The amounts of coupling agent to be used can easily becalculated. Indeed, the reaction between a coupling agent having amolecular weight M₁ and a functionality n and S—B—Li chains of molecularweight M₂ carried out in a molar ratio of 1:n will theoretically give acopolymer of molecular weight M₁+nM₂ reduced by the molecular weight ofthe coupling by-product; deviations are due essentially to traces ofimpurities or to heat, which can, for example, deactivate the S—B—Lichains (giving copolymers with a molecular weight of about M₂, as foundin the final product). The total amount of coupling agent used iscalculated in order to couple all the S—B—Li chains, but less can beused if preservation of an increased proportion of the S—B copolymer inthe final product is desired. In the present invention, the couplingratio is preferably from 70 to 95%. It is also noted that the amount ofcoupling agent may vary with the epoxy group number.

[0027] Said coupling agent is in the liquid state and is introduced inthe reactor in a solvent. Preferably, said solution contains 15 weightpercent of coupling agent, 15 weight percent of THF and 70 weightpercent of cyclohexane. It is then heated to a temperature of from 95 to100° C., preferably around 97° C., under a pressure of from 4 to 8 bars,preferably around 6 bars. The coupling reaction takes from 0.1 to 1hour.

[0028] The block coplymer formed according to this process is radial orpolybranched.

[0029] The polymer can be recovered after the polyfunctional treatingagent has formed the branched block copolymers. Recovery of the polymerscan be performed by conventional methods used for recovering polymerfrom organometal polymerisation mixtures such as treatment withmaterials containing active hydrogen such as alcohols or aqueous acids.

[0030] It is observed, quite surprisingly, that the viscosity of theresulting S—B—S product is significantly reduced when the coupling agentis a polyepoxide compound. The final product is therefore an idealcandidate for numerous applications. It has been utilised quitesuccessfully for roofing membranes, binder in road applications andfootwear applications.

[0031] The following examples illustrate some of the possible uses ofthe composition of the present invention.

Roofing Application

[0032] A composition comprising 12 weight % of S—B—S block copolymer and88 weight % of bitumen was prepared. The bitumen used in thiscomposition was bitumen A of Table III.

[0033] The coupling agent was Vikoflex 7190 that is an epoxidisedlinseed oil characterised by 9.3% oxirane and 5.8 epoxy groups per mole.The percentage of coupling of the product was 77% and the styreniccontent was 37 wt %. No oil was added to the mixture.

[0034] Comparative examples have been prepared using the same blockcopolymer and the same bitumen with the difference that SiCl₄ was usedas coupling agent. Different percentages of coupling and/or styreniccontent were used.

[0035] The product compositions and the results are presented in TableI. TABLE I 1 2 3 4 Coupling agent SiCl₄ SiCl₄ Vikoflex SiCl₄ % couplig70 93 77 96 % oil 5 −0 0 0 % styrene 31 31 37 36 Toluene solutionviscosity 19.5 28.5 19.2 29.1 (TSV) mm²/s Properties Ring and balltemperature (° C.) 118 126 132 134 Penetration @ 25° C. (0.1 mm) 58 4958 49 Cold bending temperature (° C.) −40 −38 −34 −32 Workingtemperature range (° C.) 158 164 166 166 Viscosity at 160° C. (Pa · s)3.9 4.2 3.7 5.2 Viscosity at 180° C. (Pa · s) 1.8 1.8 1.6 2 Flow at 100°C. and angle of 45°  2 h 30 (mm) 11 6 1.5 6  5 h 00 (mm) 17 8 3 8 24 h00 (mm) 250 62 5 16

[0036] The following methods have been used to measure the propertiesappearing in this application:

[0037] Toluene Solution Viscosity: ASTM-D 445 revised 86.

[0038] Ring and Ball Temperature: ASTM-D 36.

[0039] Cold Bending Temperature: DIN 52123.

[0040] Viscosity: ASTM-D 2170 revised 89.

[0041] In Table I, the product of column 1, prepared with SiCl₄ ascoupling agent, and the product of column 3, prepared with Vikoflex 7190as coupling agent, have different styrenic and oil content in order toexhibit similar toluene solution viscosities (TSV), of 19.5 and 19.2respectively. The product obtained with Vikoflex has a higher styreniccontent: normally high styrenic percentage results in an improvement ofmechanical properties but it increases the viscosity, thus making theproduct difficult to handle: this can be seen by comparing columns 2 and4. Such behaviour is not observed with the Vikoflex product that exhibitsimultaneously improved mechanical properties and low viscosity.Increasing the percentage of coupling also improves the mechanicalproperties but also increases the TSV and the viscosity, as can be seenby comparing columns 1 and 2. The product obtained with Vikoflex ascoupling agent keeps the improved properties of the products obtainedwith SiCl₄, when high percentage of coupling and/or high percentage ofstyrene are utilised, without increasing the TSV and/or the viscosity.Comparing the properties of the products of column 1 and 3 indicates asubstantial improvement in the ring and ball temperature, in the rangeof working temperatures, and quite surprisingly, at equivalentviscosities, a dramatic reduction of the flow, when Vikoflex is used ascoupling agent.

Road Applications

[0042] Two binders for road applications have been prepared, one withthe same bitumen A as in the roofing application and another one with abitumen B described in Table III. These binder products comprised 5weight percent of S—B—S block copolymer and 95 weight percent ofbitumen.

[0043] The coupling agent was Vikoflex 7190 as in the roofingapplication, the percentage of coupling was 77% and the styrenic contentwas 37 wt %. No oil was added to the mixture.

[0044] Comparative examples have been obtained using SiCl₄ as couplingagent. The product compositions and the results are summarised in TableII. TABLE II 1 2 3 Coupling agent SiCl₄ SiCl₄ Vikoflex % coupling 70 9377 % oil 5 5 0 % styrene 31 31 37 TSV mm²/s 19.5 25 19.2 Properties ofthe product prepared with bitumen A Ring and ball temperature (° C.) 8887 92 Penetration @ 25° C. (0.1 mm) 94 90 105 Viscosity at 135° C. (Pa ·s) 1.1 1.4 1.2 Elastic recovery (%) 87 95 97 Properties of the productprepared with bitumen B Ring and ball temperature (° C.) 59 59 64Penetration @ 25° C. (0.1 mm) 92 93 97 Viscosity at 135° C. (Pa · s) 1.81.8 1.6 Elastic recovery (%) 80 94 95

[0045] The elastic recovery was measured using the ASTM-6084-97technique. Comparing column 1 and column 3, it can be seen that, if thestyrenic content of the final product obtained with Vikoflex is adjustedin order to obtain the same viscosity as that of the product obtainedwith SiCl₄, all the desired properties are substantially improved withthe Vikoflex products. More particularly, the ring and ball temperatureand the elastic recovery are increased.

[0046] Comparing column 2 and column 3, it is observed that, even if thepercentage of coupling is increased for the product prepared with SiCl₄,the ring and ball temperature and the elastic recovery of the finalproducts remain substantially better for the “Vikoflex” products. Inaddition, the viscosity of the product prepared with Vikoflex remainslower. TABLE III BITUMEN A BITUMEN B 180/200 80/100 Ring and balltemperature ° C. 36 47 Penetration 0.1 mm 179 97 Viscosity at 135° C. Pa· s <0.5 <0.5 Structure: % Saturated % 6.5 5.5 Aromatics % 57.5 50.5Resins % 21 24.5 Asphaltenes % 15 19.5

[0047] The penetration was measured using the ASTM-D 5 (revised 95)method.

Footwear Applications

[0048] Two compositions have been prepared: all the constitutingcomponents and quantities were identical except for the coupling agentthat was either SiCl₄ for the comparative example or Vikoflex for theworking example. The components, quantities given in weight percent, andproperties of these two compositions are summarised in Table IV. TABLEIV COMPOSITION S—B—S low styrene 7 7 S—B—S (A) 12 12 S—B—S (B) 15 15SiCl₄ 23 — Vikoflex — 23 Oil 28 28 General purpose polystyrene 4 4 Highimpact polystyrene 4 4 CaC0₃ 7 7 Properties Melt flow g/10 min 9 13Hardness Shore — 81 78 Rebound % 31 32 Density g/cm³ 0.9811 0.9800Abrasion mm³ 130 150 Traction Rupture Mpa 6.0 4.6 Elongation % 725 670Tensile strength Mpa 3.26 3.06 (300% elongation) Tear N/mm 27.7 26.8

[0049] The following methods have been used for measuring the propertiesappearing in these examples:

[0050] Melt Flow (MI5): ASTM-D 1238 revised 89, at 190° C. and under aload of 5 kg.

[0051] Hardness Shore: ASTM-D 2240.

[0052] Rebound: DIN 53512.

[0053] Abrasion: DIN 53516.

[0054] Tensile: ASTM-D 412, D 638, D 882

[0055] Tear: ASTM-D 624.

[0056] It is observed that, all other properties being equivalent, themelt flow rate of the product of the present invention, obtained usingVikoflex as coupling agent, is much higher than that prepared withSiCl₄. The product of the present invention will thus be easier toprocess and inject to form shoe soles.

1. Use of a composition of polymer appropriated for footwear shoe solecharacterized in that it comprises a styrene-butadiene block copolymercoupled with epoxidised vegetable oils.
 2. Use of a compositionaccording to claim 1 in that the styrene-butadiene copolymer content iscomprised between 30 and 70% by weight, preferably between 40 and 60%.3. Use of a composition according to claim 2 in that the styrene contentin the styrene-butadiene block copolymer is comprised between 15 and 45%by weight, preferably between 35 to 39%.
 4. Use of a compositionaccording to claim 3 wherein the coupling agent has at least 3 epoxygroups.
 5. Use of a composition according to claim 4 wherein thecoupling agent is soja bean oil or linseed oil.
 6. Footwear compositionaccording to any of the previous claims.